It is dangerous to ignore SkRect::intersect's return value

src/gpu/GrReducedClip.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrReducedClip.h"
 
 typedef SkClipStack::Element Element;
@@ skipping 391 matching lines @@
             if (!SkRect::Intersects(stackBounds, scalarQueryBounds)) {
                 *initialState = kAllOut_InitialState;
                 if (requiresAA) {
                    *requiresAA = false;
                 }
                 return;
             }
             if (tighterBounds) {
                 SkIRect stackIBounds;
                 stackBounds.roundOut(&stackIBounds);
-                tighterBounds->intersect(queryBounds, stackIBounds);
+                if (!tighterBounds->intersect(queryBounds, stackIBounds)) {
+                    SkASSERT(0);
+                    tighterBounds->setEmpty();
+                }
                 bounds = tighterBounds;
             }
         } else {
             if (stackBounds.contains(scalarQueryBounds)) {
                 *initialState = kAllOut_InitialState;
                 if (requiresAA) {
                    *requiresAA = false;
                 }
                 return;
             }
             if (tighterBounds) {
                 *tighterBounds = queryBounds;
             }
         }
     }
 
     SkRect scalarBounds = SkRect::Make(*bounds);
 
     // Now that we have determined the bounds to use and filtered out the trivial cases, call the
     // helper that actually walks the stack.
     reduced_stack_walker(stack, scalarBounds, result, resultGenID, initialState, requiresAA);
 
     // The list that was computed in this function may be cached based on the gen id of the last
     // element.
     SkASSERT(SkClipStack::kInvalidGenID != *resultGenID);
 }